Thermocouple protection tube for use in molten metal

ABSTRACT

A shock spring provides flexibility between a Zircon protection tube for an immersion thermocouple and its mounting to reduce the possibility of breakage of the tube when it is struck by a ladle or other object.

United States Vaiden atent [54] THERMOCOUPLE PROTECTION TUBE [56]References Cited FOR USE IN MOLTEN METAL UNITED STATES PATENTS [72]Invent Park 2,218,779 10/1940 Wendt ..73/343 [73] Assignee:Barber-Colman Company, 3,309,237 3/1967 Kelchner ..73/359 Rockford,3,0l3,097 12/1961 Fritts .L ..136/232 [22] Filed: June 1970 PrimaryExaminer-Louis R. Prince 2 APPL 44,290 Assistant Examiner-Denis E. CorrAttorney-A. Richard Koch [52] US. Cl ..73/343 R, 73/359, 136/230, [57]ABSTRACT I I Cl 136/ 36 1 632 A shock spring provides flexibilitybetween a Zircon g i 034 232 protection tube for an immersionthermocouple and I I o arc 136/236 its mounting to reduce thepossibility of breakage of the tube when it is struck by a ladle orother object.

8 Claims, 6 Drawing Figures ll 5 Z4- Z2 /4 /4 Z9 7 1 2 20 I a I 37 l2 E34 20 25 23 35 :1 .a/J/ I7 I 2* 3a 33' 36 i I PAYETEDAUQ 1 I972 INVENTORCLIFFORD l Almsu AGENT BY v THERMOCOUPLE PROTECTION TUBE FOR USE INMOLTEN METAL BACKGROUND OF THE INVENTION This invention is concernedwith temperature measurement in molten metals and more particularly withmeans for reducing the possibility of breakage of fragile thermocoupleprotection tubes when they are subjected to forcible contact withanother object.

In order to continuously measure the temperature of molten metals, athermocouple or other temperature sensing device is immersed in themolten metal. Since molten metal is highly corrosive, it is necessary toprotect the sensor by enclosing it in a corrosion resistant housing thatwill withstand the temperature encountered. Fused quartz and variousrefractory ceramic materials have been found acceptable for suchhousings, but they are fragile and therefore easily broken upon contactwith another object. This invention is directed toward a solution ofthis problem.

In one application a thermocouple is enclosed in a refractory ceramictube to protect it from the corrosive action of molten aluminum in aholding furnace. These furnaces are not very large so when an operatordips a ladle into the furnace to remove dross or some of the aluminum,he is very likely to hit the thermocouple housing. Since the ceramictube is quite fragile, it is easily broken when mounted rigidly, as'itwas prior to my invention.

, SUMMARY OF THE INVENTION The present invention is based on thediscovery that breakage of a fragile thermal sensor protective housingcould be reduced by providing flexibility between the housing and. itsmounting to absorb the energy resulting from contact between the tubeand other objects. The means for providing this flexibility are simple,inexpensive and easily installed.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows the preferredembodiment of this invention and its use.

FIG. 1 is a diagramatic representation of one use of this invention.

FIG. 2 is a sectional view through an immersion thermocouple employingthis invention.

FIGS. 3, 4 and 5 are end views of insulators employed in FIG. 2.

FIG. 6 is a sectional view of the insulators of FIGS. 3, 4 and 5 withwires passing through them to show the transition from one to another.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment shownand described herein is primarily-intended for use in measuring thetemperature of molten aluminum in holding furnaces. It is to beunderstood that the invention is not limited to this preferredembodiment and that it is limited only by the scope of the claims.

The immersion thermal sensor 1 has a hot leg 2, part of which isimmersed in the molten aluminum 3 confined in a holding furnace 4, and acold leg 5, attached rigidly on a fixed mount 6 and having a headassembly 7 at its far end. A flexible armored cable 8 or otherelectrical conduit connects the head assembly 7 to a temperatureindicator or controller 9. When some of molten aluminum 3 is dipped fromthe furnace 4 as by a ladle 10, a fixed hot leg 2 is easily broken ifstruck by the ladle, as may be readily seen in FIG. 1. When resilienceis introduced into the mounting of the hot leg according to thisinvention, the hot leg may be deflected as shown in dotted lines and soreduce the possibility of breakage.

Details of the immersion thermal sensor 1 are shown in FIG. 2. Thesensing element is a thermocouple junction 11 formed by twistingtogether and fusing first ends of two thermocouple wires 12 and 13,which may be iron and constantan respectively. The wires 12 and 13 apartfrom junction 11 are insulated from each other to prevent spuriousmeasurements by lengths of elongated ceramic insulators 14 having twobores 15 and 16 lengthwise therethrough (as best seen in FIG. 3),ceramic transition insulators 17 having-two bores 18 and 19 lengthwisetherethrough (as seen in FIG. 4), and by ceramic fish spine beads 20,each having an axial hole 21 therethrough (as seen in FIG. 5). Theelongated insulators 14 are used for long straight runs, and the beads20 for bends. Each wire 12 and 13 has beads 20 strung on it where thewires must be flexed or bent so that there are always two beads side byside at such locations. When beads 20 are side by side, the holes 21 arespaced farther apart than the bores 15 and 16 in the elongatedinsulators l4, creating a misalignment between them. The transitioninsulators 17 have larger diameter bores 18 and 19 such that wires 12and 13 may pass freely from bores 15 and 16 into bores 18 and 19 andfrom bores 18 and 19 into respective holes 21 when insulators l4 and 17and the beads 20 are in abutting relationship, as shown in FIG. 6. Theends of wires 12 and 13 remote from junction 11 enter passageways 22 inrespective terminals 23 (only one of which for wire 12 is shown), wherethey are held by set screws 24. A terminal screw 25 in each terminal 23permits attachment of the sensor 1 to the external indicating orcontrolling device 9. The terminals 23 are retained in and insulatedfrom each other by a terminal block 26.

A closed end tube 27 of refractory material substantially unaffected bythe corrosive action of the molten metal 3 in furnace 4 protects thesensing element 11 from such corrosion and permits the element to belocated at any desired depth in the molten metal. In this embodiment thetube is made of zircon, a refractory ceramic, substantially unaffectedby, and not wetted by, molten aluminum. As is true of most ceramics, itis relatively fragile. The open end is cemented into one end of a pipecoupling 28. This combination forms the hot leg 2. The cold leg 5comprises a pipe elbow 29, a pipe nipple 30 and the head assembly 7enclosing the terminal block 26. In the prior art the hot leg 2 wasrigidly connected to the cold leg 5 at elbow 29.

The heart of the present invention resides in a resilient adapter orconnector 31 forming a connection between the hot and cold legs 2 and 5.In the present embodiment it comprises a helical spring 32 attached ateach end as by brazing to threaded bushings or couplings 33 and 34respectively, and a sleeve 35 of flexible material such as asbestoscloth surrounding the spring 32 and fastened to the bushings 33 and 34as by wire clamps 36 and 37. Bushing 33 is threaded into pipe coupling28 and bushing 34 is threaded into elbow 29 to complete the connectionbetween the hot and cold legs 2 and 5. The spring 32 is stiff enough tohold the hot leg 2 in substantially fixed relation to cold leg when noexternal force is applied, but is flexible enough to permit deflectionof the hot leg from the fixed relationship when it is subjected toexternal force as by the ladle 10. The sleeve 35 prevents molten metalsplashing onto and solidifying on the spring 32, thereby reducing itsresilience. It further hinders molten metal from shorting the wires 12and 13, where it would cause inaccurate readings. It also excludesmolten metal from entering the top of tube 27.

In some embodiments it may be desirable to move the sensor as from onefurnace to another. In that event the cold leg 5 would not be rigidlymounted, but could become a handle for supporting the hot leg 2 as it isbeing moved or while it is immersed in the molten metal. In either eventit forms a support for the hot leg. The use of this invention is notconfined to molten metals, but may encompass other fluids. When othermetals or fluids are encountered it may be necessary or desirable toemploy different materials in the tube 27 or other housing for thesensing element 1 1. Although a helical spring 32 has been employed inthe preferred embodiment, any other resilient means (i.e., a bellows)could be substituted therefor.

Iclaim:

1. An immersion thermal sensor comprising a sensing element, aprotective housing enclosing said sensing element, a support for saidhousing, said housing having one end adjacent the support and extendingin one direction away from said support, and a resilient connectionbetween said one end of the housing and an end of said support, saidconnection supporting said housing from said support and permittingdeflection of the housing from its normal position.

2. A sensor according to claim 1 further comprising a coupling affixedto an end of said connection separably joining the connection to saidhousing.

3. A sensor according to claim I further comprising a coupling affixedto an end of said connection separably joining the connection to saidsupport.

4. An immersion thermal sensor comprising a sensing element, aprotective housing enclosing said sensing element, a support for saidhousing, and a resilient connection comprising a helical spring betweenan end of the support and an end of said housing, said spring permittingdeflection of the housing from its normal position.

5. An immersion thermal sensor comprising a sensing element, aprotective housing enclosing said sensing element, a support for saidhousing, a resilient-connection between the support and said housingpermitting deflection of the housing from normal position and a flexiblesleeve surrounding said connection.

6. A sensor according to claim 5, said sleeve comprising asbestos cloth.

7. A sensor according to claim 5 further comprising first and secondcouplings affixed to respective opposed ends of said connection andseparably joining the connection between said housing and said support,said couplings fastened to respective opposed ends of the slegve.

A sensor according to claim 7, said connection comprising a helicalspring.

1. An immersion thermal sensor comprising a sensing element, aprotective housing enclosing said sensing element, a support for saidhousing, said housing having one end adjacent the support and extendingin one direction away from said support, and a resilient connectionbetween said one end of the housing and an end of said support, saidconnection supporting said housing from said support and permittingdeflection of the housing from its normal position.
 2. A sensoraccording to claim 1 further comprising a coupling affixed to an end ofsaid connection separably joining the connection to said housing.
 3. Asensor according to claim 1 further comprising a coupling affixed to anend of said connection separably joining the connection to said support.4. An immersion thermal sensor comprising a sensing element, aprotective housing enclosing said sensing element, a support for saidhousing, and a resilient connection comprising a helical spring betweenan end of the support and an end of said housing, said spring permittingdeflection of the housing from its normal position.
 5. An immersionthermal sensor comprising a sensing element, a protective housingenclosing said sensing element, a support for said housing, a resilientconnection between the support and said housing permitting deflection ofthe housing from normal position and a flexible sleeve surrounding saidconnection.
 6. A sensor according to claim 5, said sleeve comprisingasbestos cloth.
 7. A sensor according to claim 5 further comprisingfirst and second couplings affixed to respective opposed ends of saidconnection and separably joining the connection between said housing andsaid support, said couplings fastened to respective opposed ends of thesleeve.
 8. A sensor according to claim 7, said connection comprising ahelical spring.